Regeneration and repair are the fundamental features of the healing response. The ability to regenerate (i.e., to replace damaged tissue with healthy cells of similar type) varies among tissues and may be seen in the corneal epithelium and conjunctiva. While the healing response in and around the eye occurs primarily because of tissue repair mechanisms (i.e., damaged tissue is replaced by a newly generated fibrous connective tissue) rather than regeneration, there is substantial data suggesting that regeneration of the natural lens is possible. Ideally, the regenerated lens, with or without a suitably flexible and biocompatible polymeric lens, would have all the properties of the natural lens including clarity, protein content, histology, focusing power and accommodative ability. Optimally, corrective powers could optionally be included, later added, in combination with related mechanisms imparting ameliorative visual acuity enhancements.
Extracapsular cataract extraction with implantation of an intraocular lens (IOL) is currently the most common method for the treatment of cataracts. This procedure is less than ideal because the current synthetic intraocular lenses are unable to accommodate appreciably, and secondary opacification of the posterior capsule is a common occurrence. While intraocular implantation of multifocal or accommodating intraocular lenses (IOLs) attempt to address the need for far and near vision in the cataract patient, they are complicated by the development of posterior capsule opacification and visual dysphotopsias. Posterior capsule opacification (PCO) occurs secondary to anterior lens epithelial cell migration and myoblastic transformation and contributes to wrinkling of the posterior capsule and visual distortion.
Ideally, if a regenerated natural lens could replace a suitable biodegradeable material, the reformed lens would have the same or similar natural focusing power as the normal young lens and be able to accommodate. Alternatively, if naturally regenerating lens epithelial cells could be directed to grow in a regularly organized pattern around a suitably flexible and biocompatible polymeric lens, the resultant bilenticular system might be able to accommodate. Other and further corrections and enhacements would be within the purview of artisans, and are within the scope of the instant teachings.
Hyaluronic acid has been shown to be beneficial in wound healing in various body tissues. Hyaluronic acid in the form of Healon® (available from PHARMACIA AB, Gronigen, NL) has been used to fill the lens capsule bag following phacoemulsification (i.e., a cataract surgical procedure which uses an ultrasonic vibration to shatter and break up a cataract for removal) and irrigation/aspiration of both the natural and cataractous lens and sealing of the anterior capsule in the rabbit. However, the Healon® normally is resorbed by about one week postoperatively when the regenerating lens cells are in various stages of development. Additionally, over time the regenerated lens has had an abnormal nucleus in the form of a star-shaped opacity as the earliest lens fibers regenerated at different rates.
There is therefore a need in the art for a regenerated lens (with or without a suitably flexible and biocompatible polymeric lens) which would have all the properties of the natural lens including clarity, protein content, histology, focusing power, accommodative ability, configuration, shape and structure. There is a further need in the art for the regeneration of a clear natural lens with or without a biocompatible polymer lens in which the former may be applicable to treatment of cataract in the pediatric population and the latter suitable for adult cataract, offering true accommodation and correction of presbyopia. There is additionally a need to improve lens cell proliferation and differentiation following phacoemuslification and irrigation/aspiration. Furthermore, there is a need in the art to treat ocular disease and/or correct vision impairments without its associated complications, as for example, posterior capsule opacification.